UDN2916EB-T Ver la hoja de datos (PDF) - Allegro MicroSystems

Número de pieza

componentes Descripción

Fabricante

UDN2916EB-T

DUAL FULL-BRIDGE PWM MOTOR DRIVER

Allegro MicroSystems 

2916

DUAL FULL-BRIDGE

MOTOR DRIVER

APPLICATION NOTES

Current Sensing

To minimize current sensing inaccuracies caused by ground

trace IR drops, each current-sensing resistor should have a

separate return to the ground terminal of the device. For low-

value sense resistors, the IR drops in the PCB can be significant

and should be taken into account. The use of sockets should be

avoided as their contact resistance can cause variations in the

effective value of RS.

Generally, larger values of R S reduce the aforementioned effects

but can result in excessive heating and power loss in the sense

resistor. The selected value of RS should not cause the absolute

maximum voltage rating of 1.5 V, for the SENSE terminal, to be

exceeded. The recommended value of R S is in the range of:

RS = 0.75 / ITRIP(max) ± 50% .

If desired, the reference input voltage can be filtered by placing

a capacitor from REFIN to ground. The ground return for this

capacitor as well as the bottom of any resistor divider used

should be independent of the high-current power-ground trace to

avoid changes in REFIN due to IR drops.

Thermal Considerations

For reliable operation, it is recommended that the maximum

junction temperature be kept below 110°C to 125°C. The

junction temperature can be measured best by attaching a

thermocouple to the power tab or batwing of the device and

measuring the tab temperature, T TAB . The junction temperature

can then be approximated by using the formula:

TJ = TTAB + (2 × ILOAD × VF × RθJT) ,

where V F can be chosen from the electrical specification table

for the given level of ILOAD. The value for RθJT is approximately

6°C/W for both package styles.

The power dissipation of the batwing packages can be improved

20% to 30% by adding a section of printed circuit board copper

(typically 6 to 18 square centimeters) connected to the batwing

terminals of the device.

The thermal performance in applications that run at high load

currents, high duty cycles, or both can be improved by adding

external diodes from each output to ground in parallel with the

internal diodes. Fast-recovery ( ≤200 ns) diodes should be used

to minimize switching losses.

Load Supply Terminal

The load supply terminal, VBB, should be decoupled with an

electrolytic capacitor ( ≥47µF is recommended), placed as close

to the device as is physically practical. To minimize the effect of

system ground IR drops on the logic and reference input signals,

the system ground should have a low-resistance return to the

load supply voltage.

Fixed Off-Time Selection

With increasing values of t OFF, switching losses decrease, low-

level load current regulation improves, EMI reduces, PWM

frequency decreases, and ripple current increases. The value of

tOFF can be chosen for optimization of these parameters. For

applications where audible noise is a concern, typical values of

tOFF should be chosen in the range of 15 to 35 µs.

www.allegromicro.com

7

Share Link: